From behind his reflective wrap-around shades, Mueller spots a gap in the afternoon congestion. His electric sports car can rocket from zero to 60 in 2.3 seconds, and Mueller seems eager to demonstrate the point. “This is where we accelerate,” he says, stomping on the pedal. The torque hits like a physical blow, pinning us against the leather seats as Mueller cackles. “The moon and the near-Earth asteroids,” he continues moments later, now parked at a red light, “contain billions of tons of metal, silicon, water and ice, so we have to start using it. It seems a little farfetched to start using it now, because we just haven’t built the space economy. We haven’t got there yet.”

That is the bet behind Mueller’s Impulse Space, the Redondo Beach-headquartered startup he founded in 2021, a few months after leaving SpaceX. Just as SpaceX dominates the global launch market, Impulse wants to own what comes next: “in-space mobility,” moving satellites, cargo and eventually people after rockets drop them off in orbit. Its spacecraft are not built to blast off from Earth, but to hitch rides aboard launch providers like SpaceX, then detach and ferry payloads between orbits—and one day, Mueller hopes, to the moon, Mars and beyond.

Impulse’s selling point is not just that it can move things in space, but that it can move them quickly. Like Mueller’s all-electric Porsche, most satellites are powered by electric propulsion systems, but unlike his car these spacecraft are slow: It takes between six to 12 months for most satellites to get from low orbit, a few hundred miles above Earth, to geostationary orbit, more than 22,000 miles up. Impulse says its spacecraft will reduce that journey to a day with its chemical engines, powered by liquid methane and liquid oxygen—the cosmic equivalent of swapping ships for airplanes.

“What distinguishes us from other spacecraft is we’re about half propellant by mass when we lift off, so we can move fast,” says Mueller. “Moving fast is what our customers want.”

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Mueller’s pitch is landing at a moment when space is attracting more capital than ever. Global spending on space is projected to grow from roughly $600 billion last year to $1.8 trillion by 2035, while venture investors poured a record $55.3 billion into space startups last year. Later this week, SpaceX is expected to raise $75 billion in a record-breaking IPO, targeting a $1.8 trillion valuation. Small by comparison, Impulse has raised over $1 billion, and was valued earlier this month at $4.3 billion. Mueller, between his stakes in SpaceX and Impulse, joined the Forbes billionaires list this spring and now has an estimated $1.7 billion fortune.

But Impulse is not just racing competitors. It is racing the market itself, betting that satellites, lunar missions and military payloads will need fast transportation soon enough to justify the hundreds of millions of dollars Mueller is pouring into spacecraft built for a space economy still taking shape.

“Nobody knows what these markets are going to look like,” says space analyst Chris Quilty. “These are markets that don’t exist yet.”

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Raised in Saint Maries, Idaho, a timber town of 2,500 people an hour south of Coeur d’ Alene, Mueller grew up riding dirt bikes with cousins and learning about the timber industry from his father, a logger. In high school he saved money from unpacking boxes at the local grocer to buy his first car, a 1977 Triumph Spitfire, whose engine he fiddled with. Encouraged by a high school math teacher, Mueller studied mechanical engineering at the University of Idaho. “He came from a meager background,” recalls retired professor Terry Precht, an Idaho-native who compares Mueller’s hometown to Appalachia. “He knew how to make it happen because he’s a builder.”

In 1985, Mueller moved to Los Angeles to join aerospace conglomerate TRW as a propulsion and power engineer. He cut his teeth in the rocket division during President Ronald Reagan’s $30 billion push ($90 billion in today’s dollars) to develop space-based weaponry. Flush with government cash, scientists and engineers like Mueller could experiment. “I worked on all kinds of crazy things,” he recalls, listing chemicals he used to power rockets that are now highly regulated.

Even so Mueller became frustrated with the bureaucratic hoop jumping that came with working for a 100,000-person corporation. “I was wanting to move faster. It seemed like everything was designed by committee and there were too many people on the committee,” he recalls. “I was an entrepreneur but didn’t know it.”

He found his release with the Reaction Research Society, a quirky group of professional engineers who spent weekends bolting home-built engines to trailers in the dry lake beds of the Mojave Desert. By 2002, Mueller was tinkering with a massive 13,000-pound-thrust engine in an El Segundo warehouse. It was there that Musk, fresh from a failed attempt to buy Russian ICBMs, was led by a consultant to see Mueller’s work. “Can you build something bigger?” Musk asked Mueller, who promptly left TRW to become SpaceX’s first employee.

At SpaceX, Mueller became Musk’s engine room. As the company’s first employee, he led development of the Merlin engine that powers SpaceX’s workhorse Falcon 9 rocket, which accounted for 52 percent of all global launches and 84% of all satellite deployments in 2024, according to the American Enterprise Institute. He also oversaw propulsion development for Dragon, the SpaceX capsule that carries cargo and astronauts to the International Space Station. By the time he left in 2020, after SpaceX had largely solved the problem of getting payloads to orbit, Mueller was thinking about the question of how to move satellites around after the rockets let them go.

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The answer is taking shape inside Impulse’s 60,000-square-foot warehouse in Redondo Beach, where hundreds of engineers oversee 3D printers churning through metal alloys in glass chambers and test white-hot thrusters in sealed vacuums. Beyond the engines and chassis, Impulse produces its own radiation-hardened avionics, propellant tanks and X-band antennas. Half-completed hardware sits on shelves awaiting delivery to the next station in the engineering conveyor belt. Impulse, like SpaceX, wants to make everything in-house.

“Once you achieve vertical integration, you have better control over your cost, your schedule, and your quality,” says Mueller from his office desk. Behind him sits a bookshelf with textbooks such as Space Mission Analysis and Design and Magnetic Actuators and Sensors. Mueller flips through a graph paper notebook stuffed with scribbled engine-part designs. “I start with sketches, then I’ll typically go to CAD [computer-aided design] and then to build.” As chief technology officer, Mueller leads design of Impulse’s new propulsion systems. He manufactures prototypes of ignition parts at his offsite garage, which also houses a collection of sports cars and dirt bikes. Mueller’s man cave is “where a lot of ideas and prototypes have been born for Impulse,” says Drew Damon, one of many Impulse engineers who previously worked at SpaceX.

Impulse’s in-house push has produced two main vehicles: Mira for smaller jobs near Earth, and Helios for heavier hauls to higher orbits. Mira, a horse-sized craft that looks like a toaster with solar-panel wings, has already completed three missions. Impulse’s larger vehicle Helios, which resembles a futuristic water tank, is designed to haul payloads of up to four tons from low-Earth orbit to geostationary orbit, a distance of over 20,000 miles, in less than 24 hours. Helios is slated to complete its first mission in 2027.

Impulse’s first two Mira missions—in late 2023 and early 2025—went off without a hitch, performing a record-breaking 150-kilometer orbit raise, rendezvousing with another satellite in orbit, and depositing its clients’ CubeSats (miniature satellites) onto its intended orbital planes. During the third Mira outing earlier this year, a technical problem caused the vehicle’s star trackers to produce noisy measurements. This tricked the flight computer into over-correcting and in an attempt to stabilize itself, Mira floored the accelerator and ran out of fuel. Luckily it had already completed its satellite deployments.

Despite the hiccup, nobody’s questioning Mueller’s engineering chops or the caliber of Impulse’s team. The bigger question is whether the space economy grows fast enough to absorb the capacity that Impulse is building at great cost.

For now Uncle Sam is Impulse’s biggest demand driver, as is common in the space industry The U.S. Space Force requested $71 billion for fiscal year 2027, a 77% jump over current levels as the Pentagon embraces a far more aggressive posture in space, including President Trump’s proposed $175 billion Golden Dome missile-defense system. NASA meanwhile says it plans to establish a permanent basecamp on the moon by the end of the decade. Impulse is riding that wave. To date it has received nearly $400 million in contracts, the “overwhelming majority” of which comes from government spending, says Impulse president Eric Romo, who began his career as an MBA intern working at SpaceX before founding and selling multiple companies and working at Facebook.

On the commercial side, much depends on SpaceX’s massive Starship rocket, which can carry up to six times as much cargo as the Falcon 9 but has faced technical setbacks. For startups like Impulse, the equation is simple: more launch capacity means more satellites in orbit, and more demand for moving them once they get there. Starship completed just five launches last year, the first three of which ended in failure. That’s still a long way from Musk’s vision of Starships launching every hour by 2029. “We are built to do fine with or without Starship,” says Romo.

There’s also the potential threat from SpaceX itself. The rocket maker has plenty of capital to build its own orbital service vehicles. Will SpaceX one day enter Impulse’s lane? Mueller is unfazed. “I’m not worried, but I mean who knows?” he chuckles. “Elon was all about Mars and nothing but Mars. Then, ‘Okay, we’re going to do Starlink to help pay for Mars.’ And then it became data servers. Things change.”

A few miles from Impulse’s factory, the question of what SpaceX might do next is no longer theoretical scenery. Mueller is navigating his Porsche past SpaceX’s Hawthorne campus, where a retired Falcon 9 booster stands on the corner like a white-steel totem to the heavens.

“I don’t feel the nostalgia,” says Mueller. The lifelong engineer is far too busy optimizing the present, which includes choreographing this afternoon drive down memory lane to feature only right turns. “In rush hour, some of these left turns take two lights,” he explains, scanning the intersection ahead. “Working at SpaceX, I learned you want to plan your route carefully.”

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